Devices similar to the present type of mechanism are found in disk drives with movable heads. The linear actuator in the disk drives (sometimes called a "voice coil" movement) performs the same type basic type of control. However, the disk drive actuator was found to be unsatisfactory because the armature movement is not uniform. Rather the speed of the armature is proportional to its distance from the "target" location. Also, there is no capability for rate mode or for rate with position correction. These disadvantages have been overcome with the use of the Linear Motor Controller.
The present configuration is set up to position a quartz crystal rod under a laser beam with high positional accuracy. The accuracy obtainable is dependent solely upon an opaque graticule marking on some glass slides. As the graticule interrupts a light beam passing through the glass, optical detectors count either up or down, depending on the direction of travel of the rod. In the positional mode, the graticules are counted and used to put the rod in a position desired by the operator. In the rate mode, the speed of the rod is adjusted to a predetermined rate. In the rate-with-position-correction mode, the rate is continually updated and corrected to insure that the rod is hitting certain positional points exactly when a computer determines that these points should be hit.
Prior linear controllers, like the aforementioned disk head controller, use only a positional mode with proportional control. This means that as the head gets very close to the intended target, the speed of the head toward the target diminishes. There is no rate or rate-with-position-correction mode in these controllers.
The present device can be used in any mechanical control application where position or rate of travel is to be controlled. This includes gun traversing mechanisms, automatic welding machines, wire wrap machines, disk head controller, automobile speed controllers, automatic drafting machines, automated machine tool applications, and any other application where the linear position of a mechanical rod or beam is important. This device is very independent of the end product which it is controlling. As long as the controlled device has an input for changing the position of the device and a means of attaching a graticule position detector, this Linear Motor Controller (LMC) can control the device. This LMC can be used manually or under computer control.